1. Field of the Invention
The present invention is a regulator used for controlling fluid pressures in a downstream apparatus. The regulator can also vent excess downstream pressures to atmosphere. The body is segmented into at least three interconnected parts. In addition, a bi-directional seal design is used in conjunction with a sliding control stem.
2. Description of Related Art
Gilmore Valve Company, the assignee of the present invention, has sold shear valves and other types of regulators for many years. Examples of these prior art devices are shown in U.S. Pat. Nos. 3,917,220 and 4,493,335, both of which are included in the Information Disclosure Statement filed concurrently herewith. In order to adjust the set point for these prior art regulators, the operator was required to turn a large handle at the top of the apparatus which would compress springs on the inside of the apparatus. This was sometimes difficult at higher set points. Some prior art designs also had problems with dead bands.
Dead band is a generic term used to describe the envelope of performance when a regulator will not respond to pressure fluctuation. There are several types of dead band including forward adjustment dead band, reverse adjustment dead band, droop dead band and accumulation dead band. Generally, larger dead bands are less desirable because they degrade the sensitivity of the regulator. Smaller dead bands can also negatively affect durability. Smaller dead bands can result in chatter and/or instability under uncertain flow conditions. There is a need for a design that optimizes the dead band characteristics of a regulator to achieve a balance between sensitivity, stability and durability.
It is known in the prior art to use dual seals in conjunction with each other in order to multiply the sealing force being exerted by one of the seals. For example, in U.S. Pat. No. 3,455,566, a circular o-ring is described as a unit force multiplying seal that exerts pressure on a controlling seal that has a triangular cross section. Under compression, the shape of the circular o-ring is distorted and additional force is transferred to the second seal. However, this prior art design only works when pressure is applied from a specific direction. There is need for an improved dual seal arrangement so that the second seal will function regardless of the direction of pressure that is being applied to the other seal.
Prior art regulators are often difficult to adjust accurately at higher pressures, because the adjustment knob must push against the full force of a spring on the inside of the apparatus. In the present invention, the adjustment knob moves internal mechanisms including a small diameter control stem, not the spring.
Rotation of the adjustment knob of the present invention only requires minimum force. The higher forces and torques of prior art regulators tended to wear out the threads in the adjustment mechanism. The lower forces in the present invention minimize this wear.
Strong individuals are sometimes known to turn adjustment knobs too hard and strip the threads or ruin prior art regulators. A common solution to this problem in prior art devices is anti-rotation pins. The present invention does not have anti-rotation pins and is believed to have a unique solution to the problem of excess torque. If the adjustment knob on the present invention is turned beyond full open or full close, it merely causes the internal mechanisms including the control stem to rotate, rather than strip threads or break.
The body of the present regulator includes at least three interconnected segments. This segmented body design reduces inventory carrying costs. When an order is received, final machining of port size and type can be done for each segment. These segments are then assembled with elongate bolts to define the interconnected body. Thus the number of components required for inventory can be held to a minimum.
The present regulator has improved dead band response. If the set pressure of a regulator is adjusted upward from the forward adjustment set point, until the regulator just starts to supply, then the forward adjustment dead band (sensitivity) is the amount that the pressure increases until it stabilizes. Some prior art regulators including the Gilmore 44577 and other competitive regulators had a forward adjustment dead band in excess of 200 psi. If the set pressure of a regulator is adjusted downward from the reverse adjustment set point, until the regulator just starts to vent, then the reverse adjustment dead band (sensitivity) is the amount that the pressure decreases until it stabilizes. Some prior art regulators including the Gilmore 44577 and other competitive regulators had a reverse adjustment set point in excess of 200 psi. The present invention has less than a 50 psi forward and reverse adjustment dead band.
Droop dead band is the number of psi that the down stream pressure falls below the forward adjustment set point before the regulator starts to supply fluid. Some prior art regulators, including the Gilmore 44577 and other competitive regulators, had droop dead bands in the neighborhood of 20% of the set pressure. The present invention droop dead band is approximately 125 psi, even up to a 9000 psi set pressure.
Accumulation dead band is the number of psi that the downstream pressure increases above the forward adjustment set point before the regulator starts to vent fluid. Some prior art regulators, including the Gilmore 44577 and other competitive regulators, sometimes had accumulation dead band in the neighborhood of 20% of the set pressure. The present invention accumulation dead band is nearer to 6%.
The seal assembly in the present invention is a bi-directional pressure energized design that allows for lower friction between the control stem and the seals. The seal assembly includes both an o-ring and a seal ring. The o-ring energizes and increases the force against the seal ring which seals against the control stem.